The Des Moines Wastewater Reclamation Authority has selected the HDR architectural, engineering and consulting firm to address significant combined sewer overflow issues. HDR will evaluate and select the most appropriate treatment technologies; design and provide construction phase engineering as well as observation services for a combined sewer solids separation facility.
The project has an estimated cost of $40 million. Design plans are scheduled for completion in December 2009 and bids for construction should be received by March 2010 for a two year construction period.
The overriding goal of WRA's Combined Sewer Overflow (CSO) reduction program is water quality improvement for the Des Moines River and the downtown riverfront area, while also helping the WRA comply with an EPA consent order that such facilities be in operation by June 30, 2012. In addition, the facility will be designed to reduce adverse impacts of wet weather flows to a nearby wastewater reclamation facility.
Several solids separation alternatives will be evaluated, including a baseline alternative that would have four primary clarifiers designed for 80 million gallons per day (mgd) with physical or chemical augmentation to achieve the desired wastewater quality. Other solids removal alternatives being considered include retention treatment basins and ballasted flocculation. Treated effluent will be discharged directly to the Des Moines River.
In addition to the solids separation process, the facility is expected to include:
- an influent pump station with capacity greater than 300 million gallons per day
- a grit and screening facility to remove the substantial solids associated with combined sewer wet weather events
- a disinfection facility to reduce coliform bacteria concentrations to acceptable levels while complying with total chlorine limitations.
HDR is an employee-owned architectural, engineering and consulting firm with more than 6,800 professionals in more than 150 locations worldwide. All of them are committed to helping clients manage complex projects and make sound decisions.